APF Starlist format and requirements

To observe with the APF requires that you construct a
target list which is fed into the observing software. This
contains information about the star such
as its coordinates, but also contains when the star should
be observed and the configuration of the instrument. We
show an example below.

HD185144 19 32 21.59 +69 39 40.24 2000

pmra=598.07
pmdec=-1738.40 vmag=4.68

texp=900 I2=Y lamp=none uth=00
utm=00

expcount=1e9 decker=M do= count=1 foc=2

In each section, we discuss the various components of
this listing and the requirements. Some components are
optional.

Object ID

The name of the object is required. The name should
be an identification that can be used to reference the
object in the Simbad database. We use that database for
confirming object coordinates.

HD185144

Object coordinates and magnitude

The coordinates should be in sexagisimal format
with each component separated by spaces. A plus sign is optional for
positive declinations. Following this must be either 2000 or
the epoch for the date of observation, so 2000 is
preferred. Finally, the proper motion is specified as a pair
of keywords with the value in milli-arcseconds per year,
just as Simbad returns it. The target list must include a v band
magnitude, which we use
as a measurement of the transparency.

19 32 21.59 +69 39 40.24 2000

pmra=598.07 pmdec=-1738.40

vmag=4.68

Exposure time

The maximum exposure time in seconds should be
specified. We have an exposure meter for the guider on the
APF. This will report the photon-weighted midpoint time of
the exposure. It can also be used to curtail an exposure
after a certain number of photons have arrived on the guider.

texp=900

Calibrations During the Exposure

We have two flags for calibrations. One of these
flags selects the iodine cell and can have a value of "Y" or
"N". The second is a placeholder for taking a ThAr exposure
before the exposure and must be "none".

I2=Y lamp=none

Scheduling

The preferred time of the night of that the exposure
should be taken is expressed in UT hours and minutes. The
hours and minutes are separate key-value pairs.

uth=00 utm=00

Exposure Meter Value

A total number of counts on the guider can be
requested as a way to terminate the exposure. A total count
of one billion yields a signal to noise of 100 or so
spectrum. If the requirements are that the exposure run the
full exposure time, an exposure count of a 100 billion
should be more than sufficient. The final number of photons
counted by the guider will be recorded in the header.

expcount=1e9

Decker

The aperture used for the opening of the spectrometer
is specified by a single letter. Below we list the decker codes
with the sizes in arcseconds

K - 1 by 12 arcsec

L - 2 by 12 arcsec

M - 1 by 8 arcsec

B - 2 by 8 arcsec

W - 1 by 3 arcsec

T - 2 by 3 arcsec

S - 0.75 by 8 arcsec

N - 0.5 by 8 arcsec

O - 8 by 8 arcsec

decker=M

Pointing Check

The standard alignment process is to place the
brightest object in the 22 arcsecond search radius on the slit. To perform a
pointing check and then require a 3 arcsecond search, put
any character after the = in the statement below.
do=no or do=0 will still perform the pointing check.

do=

Optional

Additional Exposures

By default, the software will only take one
exposure, in effect count=1. By specifying count=2, two exposures
will be taken. Large numbers of exposures on the same target
can be tricky because of the requirements for the telescope
shutters. Please contact the APF staff before attempting
such an observation.

count=1

Optional

Focus check

By default, the APF will check the focus on objects
that are apparently bright enough. This can be turned off to
speed up the observing process. The brightness requirement is that
frame rate on the guider one image per second or
faster. This focus check measures the FWHM of the image on
the guider at the current focus and on either side. If the
offset is too large, then a focus sweep of seven positions
will be run. Setting foc=2 forces an actual
focus measurement. Setting foc=1 forces the
focus check, in case the default behavior is changed to turn
off the focus check.